Recognize Trogon chionurus as a separate species
from Trogon viridis (2)

Effect on SACC: This would treat an
existing species, Trogon viridis,
into two species.

Background: Our current SACC note
is as follows:

2.
Ridgely & Greenfield (2001) considered the subspecies chionurus of the Chocó region to be a separate species from Trogon viridis; followed by Hilty (2003); SACC proposal
to recognize this split did not pass because of insufficient published data.
Genetic data (DaCosta & Klicka 2008) suggest that chionurus is more closely related to T. bairdii than either are to Amazonian T. viridis. Proposal needed. Sibley & Monroe (1990) considered Trogon viridis to form a superspecies
with Central American T. bairdii, and
suggested that they might be conspecific. Proposal needed.

See SACC proposal 49 for a summary of
previous arguments pro and con.A
one-sentence summary of the previous arguments might be although chionurus differs from viridis in voice and plumage, the vocal
differences have not been adequately quantified or documented (in fact, published
descriptions are contradictory).You can here samples of both at Xeno-Canto – I am impressed with the
differences in rhythm: chionurus and viridis(but I also hear lots
of variability – browse Trogon viridis.

New information: DaCosta & Klicka
(2008) published a gene-based phylogeny of the genus that included samples of bairdii (2), viridis from Amazonia (12), and chionurus
from W. Ecuador and Panama (2).They sampled 1 mitochondrial gene, ND2, and 1041 base pairs, of which
557 were phylogenetically informative.They found strong support (99% maximum likelihood bootstrap, 100%
Bayesian support) for the sister relationship between chionurus and bairdii, as
well as strong support for Amazonian viridis
as the sister to these two.See Prop. 378 for tree.

Analysis and
Recommendation:With genetic support
from only a single, mitochondrial gene as the basis for the relationship, one
could argue that the tree is only a gene tree, not a species tree, or that the bairdii-chionurus relationship is due to incomplete lineage-sorting, or
even that hybridization between bairdii
and chionurus produces the
result.Nonetheless, combined with
the qualitative vocal data, I think that published evidence is sufficient for a
change in species limits, so I tentatively recommend a YES.

Literature Cited:

DaCOSTA, J. M., AND J.
KLICKA. 2008. The Great American Interchange in birds: a phylogenetic
perspective with the genus Trogon.
Molecular Ecology 17: 1328-1343.

Note on English names:Ridgely & Greenfield (2001) coined
“Western White-tailed Trogon” for chionurus
and “Amazonian White-tailed Trogon” for viridis,
and this was followed by Hilty (2003) and Gill & Wright (2006).I think that represents a degree of
establishment that justifies starting with them as “status quo” if the proposal
passes.However, Cory (1919)
restricted White-tailed to chionurus
and called viridis
“Green-backed.”These are actually
very nice names.“Chionurus” means
“snow-tailed”, and the larger amount of white in the tail of chionurus is one of the differences
between the two taxa; and there is also the nice parallel between the English
and scientific names.“Green-backed” also points to another major plumage difference between
the two (blue back in chionurus) and
is also reflected, somewhat, in the scientific name viridis.Also, those
long compound names are fairly unpopular, despite their ability to imply
relationships.And in this case,
with bairdii likely the sister to chionurus, they are actually misleading
as to relationships.Finally,
“Western” and “Amazonian” are fairly insipid and not entirely accurate because
a highly disjunct population of viridis
is found in the Atlantic Forest region. Therefore, I propose we use these
shorter, more accurate, more venerable names as the status quo (therefore
requiring a proposal the longer compound names could be instituted by
proposal), but I’d like to take a poll of our English-first members to see if
they like this.

Additional Note on
English names (added 6 May 09):Frank Gill pointed out to me that the
illustrations in Ridgely & Gwynne (1989), Ridgely & Greenfield (2001),
and HBW show chionurus as having a
bright green back.This is
evidently an error.Our recent
specimens from Panama have unambiguously violet-blue backs, as illustrated
correctly by Restall et al. (2006).Wetmore (1968) indicated that some individuals may have green in the
center of the back, but I cannot find any evidence for all-green backs.

Van Remsen, November 2008

Comments from Zimmer: “YES.Vocal distinctions between these two
have been noted for some time, and there are plenty of qualitative descriptions
out there, as well as published and internet-searchable examples of recordings.These agree well with the DaCosta &
Klicka genetic data, which places chionurus
as closer to bairdii, a relationship
that would have been predicted on vocal and morphological characters
alone.I think Van’s suggestions
regarding English names (“White-tailed” reserved for chionurus, and “Green-backed” for viridis) are excellent.”

Comments
from Robbins: “YES, again web-based vocal data support the Klicka et al.
genetic conclusions. I fully support Van’s English name suggestions.”

Comments
from Stiles: “YES, for reasons stated by Van and Kevin.I also prefer the English names
suggested by Van – I dislike three-word monsters, hyphenated or not, if simpler
alternatives are available.”

Comments
from Jaramillo: “YES – Song, morphology and genetics all line up to
clarify the relationship here. Kudos to Van for suggesting some simple names,
rather than multi-word monsters, so yes Green-backed and White-tailed work
well!